The present invention concerns a blood cleaning apparatus for removing unnecessary metabolic end products such as urea, uric acid and creatinine, thereby cleaning blood, as well as an artificial kidney using the same mechanism.
An artificial kidney is used as an artificial organ for patients suffering from renal insufficiency whose renal functions for discharging unnecessary metabolic end products in blood as urine are deteriorated or lost, and this is adapted for cleaning patient""s blood by separation membranes to substitute the natural renal functions to some extent.
A blood cleaning apparatus is incorporated in the artificial kidney, and the cleaning apparatus is classified into three types, namely, a dialysis type blood cleaning apparatus using dialysis membranes, a filtration type blood cleaning apparatus using ultrafiltration membranes and a plasma separation type blood cleaning apparatus using microfiltration membranes.
The dialysis type blood cleaning apparatus is referred to as a dialyzer in which hollow fibers made of dialysis membranes are disposed, and blood is caused to flow to the inside while a dialysis liquid is caused to flow on the outside of the hollow fibers, so that unnecessary metabolic end products in blood having relatively small molecular weight up to several thousands, such as urea, uric acid and creatinine are discharged outside of the hollow fibers to clean the blood.
The filtration type blood cleaning apparatus has hollow fibers formed of ultrafiltration membranes disposed therein, in which an trans-membrane pressure difference is exerted between the inside and the outside of the hollow fiber, instead of using the dialysis liquid, blood is caused to flow inside the hollow fibers and form a negative pressure at the outside thereby conducting filtration of blood at negative pressure or form a positive pressure in the inside thereby conducting filtration of blood at positive pressure, so that low molecular weight proteins such as xcex22-microglobrin having molecular weight up to several tens thousands are removed.
Further, the plasma separation type cleaning apparatus is adapted to separate blood into blood cell ingredients and plasma ingredients by a plasma separator equipped with microfiltration membranes, extract the plasma ingredients, discard the plasmas and replace them with clean plasmas.
However, when blood is cleaned by the dialysis type blood cleaning apparatus, dialysis liquid is required by as much as 150 to 200 liters in dialysis 1 trial in order to always exchange the dialysis liquid with the fresh one, to cause a problem of the size of the apparatus which is inevitably increased.
Further, when blood is cleaned by the filtration type blood cleaning apparatus, a supplementary liquid is supplied to veins which return cleaned blood to a body for supplementing filtrates removed from the blood. Since the supplementary liquid is directly mixed to the blood, it should have a composition approximate to that of the plasmas and be kept in a sterile state, which involves a problem of troublesome aspect handling and increased cost compared with blood dialysis.
Further, when the blood is cleaned by the plasma separation type blood cleaning apparatus, a great amount (from 2 to 3 liter) of plasmas is required. In addition, plasma preparations are always lacking in Japan and are extremely expensive, as well as they involve a problem of causing side effects such as hepatitis and allergy as complications.
In addition, when any type of the blood cleaning apparatus is used, since the time required for cleaning blood in a whole body is as long as from about 5 to 6 hours for 1 session, and the blood cleaning operation must be conducted about three times a week, namely, every other day. This constraint in view of time imposes a considerable burden on the quality of life of patients, and greatly restricts patients"" social activities.
Further, some pharmaceutical solutions have to be supplied in any of the blood cleaning apparatus. For example, a large amount of dialysis liquid and supplementary liquid are used for dialysis type and filtration type blood cleaning apparatus, or expensive plasma preparations are used in the plasma separation type blood cleaning apparatus. So, monitors for controlling the supply conditions or controllers for regulating the flow rate of them are required, resulted in making the apparatus more complicated and expensive.
On the other hand, a kidney of a healthy body conducts ultrafiltration about 180 liters of blood through about one million of glomerulus per day, and discharges from 1 to 2% of water content together with unnecessary metabolic end products to the outside of a body and absorbs from 98 to 99% of remaining water again together with serum electrolytes. In glomerulus, a filtration amount is 125 cc/min and a discharge amount to the outside of the body is 2 cc/min.
Then, if the function identical to that of the kidney of the healthy body can be reproduced, blood can be cleaned with no requirement for the pharmaceutical liquid at all.
Then, the technical objective of the present invention is to enable cleaning of blood at home during sleeping time, without requiring any pharmaceutical liquid at all, in a small and simple structure in the similar manner as in the kidney of the healthy body.
The present invention concerns a blood cleaning apparatus to be used in an artificial kidney for cleaning blood taken from a body, and circulating it back to the body. It comprises, in a casing equipped with a blood inlet on one side and a blood cell ingredient outlet on the other side, a centrifugator having a rotary cylinder for exerting a centrifugal force on blood to separate them into blood cell ingredients and plasma ingredients. A metabolic end product separation chamber, having a cylindrical ultrafiltration membrane for removing water, serum electrolytes and unnecessary metabolic wastes from the plasma ingredients collected to a portion near the center. Then, a water re-absorbing module comprising hollow fiber dialysis membranes for flowing concentrated plasma ingredients from which water, serum electrolytes and unnecessary metabolic end products have been removed by the cylindrical ultrafiltration membrane and re-absorbing the water, serum electrolytes and unnecessary metabolic end products taken into the separator chamber, substantially in a coaxial arrangement.
The term xe2x80x9cblood cell ingredientsxe2x80x9d used in the present specification mean not only the blood cell ingredients in the strict sense, but mean those mainly comprising blood cell ingredients taken out of the blood. In the same manner, the term xe2x80x9cplasma ingredientsxe2x80x9d not only mean plasma ingredients in the strict sense but mean those mainly comprising plasma ingredients taken out of blood.
According the present invention, blood flown from the blood inlet into the casing flows from one end to the other end thereof and is passed through the inside of the rotary cylinder via a centrifugator and separated centrifugally. In consequence, blood cell ingredients are collected near the outer circumference while the plasma ingredients are collected near the center, and the blood cell ingredients, when reach the other end, are introduced from the blood cell ingredient outlet formed to the casing to the outside.
A metabolic end product separation chamber comprising a cylindrical ultrafiltration membrane is formed at the center of the rotary cylinder and, when a differential pressure of about 100 mmHg is exerted between the inside and the outside of the chamber, unnecessary metabolic end products such as urea, uric acid, creatinine in the plasma ingredients, as well as water content and serum electrolytes are taken into the metabolic end product separation chamber and cleaned, while the plasma ingredients in which serum proteins are concentrated reach the other end of the casing during flow of the plasma ingredients to the other end of the hollow fiber membranes.
When the concentrated plasma ingredients are introduced to the inside of the hollow fiber dialysis membranes of the water re-absorbing module transferred to the metabolic end product separation chamber, water and the serum electrolytes, among water, serum electrolytes and unnecessary metabolic end products taken into the metabolic end product separation chamber, are allowed to permeate into the hollow fiber dialysis membranes and re-absorbed and remained in the metabolic end product separation chamber by the difference of the concentration of serum protein (albumin) between the inside and the outside of the hollow fiber dialysis membranes.
When the plasma ingredients diluted to an ordinary concentration by passing through the water re-absorbing module and blood cell portions taken previously are mixed, cleaned blood can be obtained.